sysdeps/unix/sysv/linux/aarch64/cpu-features.c

   1 /* Initialize CPU feature data.  AArch64 version.
   2    This file is part of the GNU C Library.
   3    Copyright (C) 2017 Free Software Foundation, Inc.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <cpu-features.h>
  20 #include <sys/auxv.h>
  21 #include <elf/dl-hwcaps.h>
  22
  23 #if HAVE_TUNABLES
  24 struct cpu_list
  25 {
  26   const char *name;
  27   uint64_t midr;
  28 };
  29
  30 static struct cpu_list cpu_list[] = {
  31       {"falkor",         0x510FC000},
  32       {"thunderxt88",    0x430F0A10},
  33       {"thunderx2t99",   0x431F0AF0},
  34       {"thunderx2t99p1", 0x420F5160},
  35       {"generic",        0x0}
  36 };
  37
  38 static uint64_t
  39 get_midr_from_mcpu (const char *mcpu)
  40 {
  41   for (int i = 0; i < sizeof (cpu_list) / sizeof (struct cpu_list); i++)
  42     if (strcmp (mcpu, cpu_list[i].name) == 0)
  43       return cpu_list[i].midr;
  44
  45   return UINT64_MAX;
  46 }
  47 #endif
  48
  49 static inline void
  50 init_cpu_features (struct cpu_features *cpu_features)
  51 {
  52   uint64_t hwcap_mask = GET_HWCAP_MASK();
  53   uint64_t hwcap = GLRO (dl_hwcap) & hwcap_mask;
  54
  55   register uint64_t midr = UINT64_MAX;
  56
  57 #if HAVE_TUNABLES
  58   /* Get the tunable override.  */
  59   const char *mcpu = TUNABLE_GET (glibc, tune, cpu, const char *, NULL);
  60   if (mcpu != NULL)
  61     midr = get_midr_from_mcpu (mcpu);
  62 #endif
  63
  64   /* If there was no useful tunable override, query the MIDR if the kernel
  65      allows it.  */
  66   if (midr == UINT64_MAX)
  67     {
  68       if (hwcap & HWCAP_CPUID)
  69         asm volatile ("mrs %0, midr_el1" : "=r"(midr));
  70       else
  71         midr = 0;
  72     }
  73
  74   cpu_features->midr_el1 = midr;
  75 }